In Redis, the ZCARD command returns the cardinality (number of elements) of a sorted set.

Syntax

The syntax goes like this:

ZCARD key

Example

Suppose we create a sorted set like this:

ZADD scores 220 user:1 110 user:2 330 user:3 550 user:4

Result:

(integer) 4

In my case the sorted set didn’t exist, and so it was created and the four elements were added as specified.

We can now use the ZCARD command to find out how many elements are in the sorted set:

ZCARD scores

Result:

(integer) 4

As expected, there are four elements in the sorted set.

Let’s add two more elements:

ZADD scores 440 user:5 660 user:6

Result:

(integer) 2

And now let’s run ZCARD again:

ZCARD scores

Result:

(integer) 6

Now there are six elements in the sorted set.

When the Key Doesn’t Exist

If the key doesn’t exist, ZCARD returns zero:

ZCARD nonexistentkey

Result:

(integer) 0

In this case, nonexistentkey doesn’t exist and so the command returned zero.